On a small note, I made a few discoveries regarding the unused bg scrolling while exploring the differences between these two revisions. They are:

1) These bg prove that 09Z was worked on.
2) This proves there was a later Wood Zone than we have in our beta [the scrolling bg is missing in beta, ALSO, it would 100k ugly with the current beta bg!
3) I found by mistake, that in beta, WZ is SCROLLING! The code for the scrolling doesn't work, but 100k at the debug camera coords :D Imagine the later WZ...

Now, with the differences:

Sonic 2 Rev 00 and Rev 01 differences.

I covered *ALL* differences, so stfu about pigs in CNZ etc.

I'm skipping the different jump/branch absolute addresses, for obvious reasons.

0x2ad7a/0x2ad78 - a bugfix in rev 01 (fixes the code for a vertical/diagonal spring from CNZ that you hold down jump on to pull back further). this code was inserted in rev 01:
0x2af72/0x2af7a - the same bug fix, for the second time, in a different part of the code

Update: the code somehow disables the spring code when you're dead. Tested in both Rev 00 and Rev 01, we haven't found the difference.

Basically, the code is like:

if (Sonic/Tails == dead) dont_spring;

locret_2AD78:
rts

loc_2AD7A:

cmpi.b #4,$24(a1)
bcc.s locret_2AD78

and the second bugfix:

locret_2AF78:

rts

loc_2AF7A:
cmpi.b #4,$24(a1)
bcc.s locret_2AF78

====================

0x12000/0x11fd4 - A bugfix in Ring Object in Rev 01. Prevents from flagging (flagging is in the later, unedited code), that player got the 100 and 200 rings 1up, when he actually didn't get it (because of the lives overflow).

The $030a object is a collision switch. I have no idea why Sega changed it though. As Gunner112k said: "The first thing I tried to do in this ROM is to go to EHZ Act 2 and go to that fucking secret wall that has been haunting my life forever. IT WORKED.

(I never told people about that, but in the rev 01 ROM you could never get through that secret wall, and I originally owned 2 Sonic 2 carts, one that you could get through and one that you couldn't. So that means I had this rev 00 for so long.)"